The following abbreviations are herewith defined, at least some of which are referred to within the following description of the state-of-the-art and the present invention.
OLT Optical Line Terminal
ONU Optical Network Unit
PON Passive Optical Network
QoS Quality of Service
ToR Top of Rack
Data centers have been in use for many years, and their extensive use and designed capacity continues to increase. A data center is a facility that contains computing or communications equipment, and frequently a large amount of such equipment, that may form a data mass storage facility or part of a telecommunications network. The data center equipment may be segregated in one large room, but may also be distributed throughout several rooms or even in separate buildings, for example to keep the entire data center from being destroyed by a single fire. Many large racks of equipment such as servers may be present in a data center. As might be expected, there is a need to provide for communication between these devices.
Where equipment is mounted in racks, there is often also an access switch connecting all of the devices in the rack and providing for external communication as well. This may be referred to as a ToR (top of rack) switch. In describing the present invention, the term “access node” will be used as there is no requirement that the servers or other data center equipment being supported in this fashion is actually mounted in a physical rack or chassis along with other devices communicating through a given access node. For convenience the collection of devices serving in the data center in this manner may be referred to as the access layer of the data center network.
A relatively small number of routers may be employed in the data center and these may be referred to as core routers or generally as the core layer of the data center network. In between the network core or core layer devices and the many access nodes of the access layer there is frequently an aggregation layer. An aggregation node may be a switch that handles the traffic between a number of access nodes and a core router. An aggregation node aggregates traffic from the access nodes such the core routers do not have to be connected to each of them individually.
An access node such as a ToR switch therefore regularly communicates with the core layer of the data center network via a primary aggregation node. It is important, however, to have at least one redundant path to the core layer in case the primary aggregation node or a communication link through it should fail. A secondary aggregation node is for this reason highly desirable. The secondary aggregation node provides and alternate path to the core layer and is available to perform this function when the primary aggregation node fails or is taken out of service for maintenance. In most cases the secondary aggregation node will be similar or identical to the primary aggregation node. In a typical data center network, there is a secondary aggregation node for each primary aggregation node. Redundancy may also be provided at the core layer in similar fashion, with each primary and secondary aggregation node in communication with at least two core routers.
As might be apparent, a tertiary node would further reduce the likelihood of an interruption in network communications, but normally the cost of another device that would spend most of its time in stand-by mode is prohibitive except for the most sensitive applications. In fact, the need for a secondary node to back up each primary node also represents a major cost that many operators would like to reduce.
Accordingly, there has been and still is a need to address the aforementioned shortcomings and other shortcomings associated with providing communication path redundancy in data center networks. These needs and other needs are satisfied by the present invention.